Compression ignition engines

ABSTRACT

A method and arrangement of supplying a supplementary fuel ( 8 ) to a compression ignition internal combustion engine wherein an air supply ( 3 ) to the engine is first caused to pass through a natural vortex creator ( 1 ), and a supply of supplementary fuel ( 8 ) to the engine is supplied into a low pressure area the natural vortex ( 1 ) which provides a substantially constant ratio of supplementary fuel to main fuel through varying load conditions.

TECHNICAL FIELD

[0001] This invention relates to engines of a type often referred to as“diesel engines” but which are more generally described as compressionignition internal combustion engines.

BACKGROUND ART

[0002] While such engines use “diesel” as a fuel, such fuel can beusefully supplemented by other fuels in certain circumstances.

[0003] This invention relates to a fuel supplementation process andmethod and to an arrangement for using supplementary fuels in engines ofthis type.

[0004] Characteristics of this type of engine include a main fuelinjection system, means to change an amount of main fuel being injectedinto the engine in response to load demands on the engine, and an airsupply. This type of engine works best with an approximately constantpressure cycle which provides a relatively flat torque curve andgenerally low specific fuel consumption. However this ideal is notreadily achieved. One factor in this is that in order to achieve areliable and instant ignition requires a fuel with a high cetane ratingbut in order to then achieve a long slow burn requires a fuel with a lowcetane rating. To achieve reliable ignition with a subsequent long slowburn then essentially requires two different fuels. This is where fuelsupplementation can be very advantageous where a main fuel is a fuelwith a high cetane rating and the subsequent supplementary fuel is afuel which is high octane and low cetane rating.

[0005] It is currently known to provide some fuel supplementation byadding supplementary fuel into an air supply where a “diesel” orcompression ignition engine is turbo charged.

[0006] However, one of the difficulties that currently exists is thedifficulty of ensuring that there is an appropriate ratio ofsupplementary fuel and air through changing load conditions.

DISCLOSURE OF THE INVENTION

[0007] In accordance with this invention, I have found that there isvery significant advantage achieved by providing that an air supply fora compression ignition type engine be drawn through an arrangementeffecting a natural vortex with a low pressure center core with such airand then connecting the low pressure core of any such vortex formed witha supply of supplementary fuel so that the supplementary fuel will bedrawn in to the low pressure core of the vortex and thereby be suppliedthrough an air intake of the engine.

[0008] Such an arrangement I have surprisingly discovered has anadvantage that a beneficial ratio of air and a supplementary fuel ismaintained by the characteristics of the natural vortex through changingload conditions.

[0009] This is in contradiction for instance with more traditionaltechniques used to effect control of proportionality.

[0010] In this way then, it is found that the ratio of supplementaryfuel to main fuel supply can remain more constant through changing loadlevels even though the engine speed and the air being drawn into theengine as a result of that engine speed will not vary substantiallythrough such changing load levels.

[0011] This has a significant advantage that through an operating cycleof an engine with changing loads that the ratio will be kept such thatpre-ignition that might otherwise be caused by an excess ofsupplementary fuel will be reduced. It also has the advantage that ahigh octane fuel can be used as the supplementary or auxiliary fuel. Theadvantage of this is that once ignition has been effected through thecompression of the main fuel, the slower burning high octane fuel willextend a burning period contributing to a more extended constantpressure through the burning cycle.

[0012] In one form then, the invention can be said to reside in a methodof supplying a supplementary fuel supply to a compression ignitioninternal combustion engine, which includes the step of having an airsupply to the engine first caused to pass through a natural vortexcreator, and effecting a supply of supplementary fuel to the engine byintroducing supplementary fuel into a low pressure area within a centreof any natural vortex adapted to be created by the vortex creator.

[0013] A characteristic of such engines is that they have their speedconstrained by a governor with increase or decrease in power beingachieved by an increase or decrease in fuel being injected into theengine with substantially the same airflow being maintained. Thishowever means that there will be relatively minor changes in air flowrates in response to load output changes. My discovery has been that byuse of the natural vortex the amount of supplementary fuel being inpreference, the supply of fuel in fluid form is provided at asubstantially constant pressure so that the amount of fuel beingsupplied into the low pressure region of the vortex will be inproportion to such low pressure and this in turn will result in arelatively constant ratio of fuel to air being supplied to a downstream“diesel” engine.

[0014] In preference, the fuel being a fluid is a gas although liquidfuels can be used in other instances where there is a preliminaryvaporisation by use of a second natural vortex creator.

[0015] There is advantage in providing a supplementary fuel as a gas inthat this then provides a higher octane fuel which is then mixed with alower octane fuel so that there is a longer burn rate.

[0016] However, there can be other reasons to have a different fuel forinstance where the supplementary fuel is hydrogen. This can provide forextremely clean or environmentally good outputs while there may be someloss in efficiency which however is acceptable. The advantage of theinvention in providing reliable main fuel to supplementary fuel ratiosin varying load conditions is even more useful with such a gas wherehigh supplement to main fuel ratios are desirable.

[0017] In experiments conducted so far, it is found that the balance offuels should be such that the total mixture is slightly lean forinstance, a ratio of 20:1 as compared to perhaps a stoichiometricmixture of 16: which is the ratio for LPG.

[0018] The advantages of this arrangement in a preferred example offerat least one or more of the following; namely, additional poweravailable from an existing engine, lower exhaust temperatures thatotherwise would be expected, less fuel and oil contamination, smootherrunning and costs savings.

[0019] The creation of a natural vortex is possible using appropriatelyshaped vanes or apertures passing through a conduit aligned so as tocause the air to be drawn through these to form a spiral path. A naturalvortex is one where a center of the vortex is at a lower pressure thanits outer parts. This is in contrast to a

[0020] Prior examples of gas supplementation have been traditionally ofwhat is called “a gas fumigation type” where at a selected load on the“diesel” engine, gas is introduced into the intake manifold in order toincrease the power. An example of this is available currently on theInternet at the URL being www.bullydog.com. or there is a system knownas “torque master system” for trucks sold under the registered trademark “CATERPILLAR”.

[0021] Under such previous techniques, a supplementation rate of 30%supplementary fuel by weight as compared to a total fuel being suppliedhas been accepted by the industry as a practical upper limit in thathigher supplementation has resulted in pre-ignition effects which makethis increase unacceptable.

[0022] With the current invention and in relation to the embodiment,supplementation up to 75% of the total fuel provided has been found tobe possible without the pre-ignition effect. There has also beenimprovement in engine efficiency with exhaust temperatures lowered inseveral trials by some 40° C.

[0023] In a further form then the invention can be said to reside in amethod of supplying a fuel supply to a compression ignition internalcombustion engine which includes having an air supply to the enginefirst caused to pass through a natural vortex creator, and effecting asupply of supplementary fuel to the engine by introducing supplementaryfuel into a low pressure area within a central area of any naturalvortex being created by the vortex creator.

[0024] In preference the main fuel supply is of a high cetane rating andthe supplementary fuel is of high octane rating.

[0025] In preference the supplementary fuel is being provided at asubstantially constant pressure to the low pressure area within acentral area of a natural vortex.

[0026] In preference the supplementary fuel is first supplied as aliquid which is introduced into a low pressure area of a second naturalvortex creator with a low pressure center core which is arranged toeffect a natural vortex with air being drawn through it by the enginewhich then in turn fed as a vapour into the low pressure area of avortex created by the first said natural vortex creator as thesupplementary fuel.

[0027] In a further form the invention can be said to reside in acompression ignition internal combustion engine including in its airsupply a natural vortex creator with a conduit connecting an outlet ofthe vortex creator with an air inlet of the engine, a conduit connectinga source of supplementary fuel with the vortex creator so as to have anoutlet of the said conduit communicating with a low pressure center of avortex.

[0028] In a further form the invention can be said to reside in acompression ignition internal combustion engine including at least onepiston within a cylinder, a main fuel injector to effect injection offuel into each respective cylinder, means to effect a change in quantityof main fuel being injected into the cylinder in response to change inload applied to the engine, a conduit connecting an outlet of a naturalvortex creator with an air inlet of the cylinder of the engine, aconduit connecting a source of supplementary fuel with the vortexcreator with its outlet communicating with a low pressure center of thevortex creator.

[0029] In a further form the invention can be said to reside in acompression ignition internal combustion engine including at least onepiston within a cylinder, a main fuel injector to effect injection offuel into each respective cylinder, means to effect a change in quantityof main fuel being injected into the cylinder in response to change inload applied to the engine, a conduit connecting an outlet of a naturalvortex creator with an air inlet of the cylinder of the engine, aconduit connecting a source of supplementary fuel in gaseous form withthe vortex creator with its outlet communicating with a low pressurecenter of the vortex creator, means connecting a source of thesupplementary fuel as a liquid to a low pressure area of a secondnatural vortex creator which is arranged to effect a natural vortex withair being drawn through it by the cylinder, a conduit connecting anoutlet of the second natural vortex creator to a low pressure area ofthe first said natural vortex creator.

BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The invention will be better understood when described withreference to an embodiment, and accordingly this is described with theassistance of drawings where:

[0031]FIG. 1 is a schematic layout illustrating the way in which avortex creator is coupled in an airflow stream through to a “diesel”engine;

[0032]FIG. 2 is a part cut away of a vortex creator with an inlet tubefor the supplementary fuel supply;

[0033]FIG. 3 is a part cut away perspective view of a vortex creatorincluding a gas input;

[0034]FIG. 4 is a part cut away of a different view of the vortexcreator showing in this case curved vanes which direct air into anatural vortex formation; and

[0035]FIG. 5 is a cross sectional view showing dimensions of the partsproviding for the vortex creation.

BEST MODE FOR CARRYING OUT THE INVENTION

[0036] Referring in detail to the drawings, and in particular to FIG. 1,there is a natural vortex creator 1 which is positioned in line from anair inlet filter 2 which has a passageway 3 directing air into thevortex creator 1 which thereafter is connected by passage 4 through tomanifold 5 of a “diesel” engine 6.

[0037] A low pressure gas (LPG) supply which holds gas in liquid form isshown at 8 and this is connected via conduit 9 through solenoid operatedvalve 10 to a liquid to gas converter at 11. The liquid to gas converterthen supplies gas through conduit 12 at a relatively constant pressureso that this is fed into a low pressure center of any natural vortexthat is formed within the vortex creator 1. The vortex creator itself isshown in greater detail in FIG. 2 through to 5, and consists of aplurality of vanes such as is shown at 13 which assist to provide apreliminary circular path to air being introduced in the direction 14 sothat the air then passes into channels shown at 15 typically which iseach defined by vanes such as at 16 which are in arcuate form and chosenso as to provide the air that passes through this into a central areawill thereafter follow and be caught within a natural vortex with itscentripetal effect being tapped.

[0038] Such a vortex which is variously referred to as a centripetal ornatural vortex is to be compared with an alternate type vortex whichmight be called a centrifugal vortex but such an alternate effectgenerally will not have a low pressure center.

[0039] Such distinctions however may be academic in practise where somecharacteristics of both may be exhibited in a formation. For this reasonit is perhaps for the sake of accuracy better to refer to the naturalvortex where there is a low pressure center at its core and where thisis being used for the purposes of this invention. Therefore while theterm centripetal vortex has been used in some instances it is better tosay that the vortex is having its centripetal component being used andwe have used the term “natural vortex with a low pressure center” todistinguish the characteristic required.

[0040] The vortex might be distinguished by reference to a centripetalor natural vortex providing a low pressure at its centre.

[0041] There are known devices to provide a centripetal vortex but wehave described once instance only of this which has been found toprovide good effect.

[0042] According to this invention and this embodiment in particularhowever, air is drawn through such a vortex creator so as to cause a lowpressure to be caused at the centre of such a vortex, and conduit 12 hasits opening as is shown specifically in FIG. 5 so as to be located atthe relative centre 17 so that it will connect with the lowest pressureposition of the vortex that might be formed by the air passing throughthe channel between the vanes 16 and thenthrough a downstream passageinto the “diesel” or compression ignition internal combustion engine.

[0043] Using this arrangement to effect a control of the degree ofmixing of air with gaseous fuel has shown itself to provide significantreliability in respect of such ratio, especially over a reasonable rangeof power demands and this has had the advantage of being able tomaintain performance in a over a range of power demands.

[0044] Hitherto this has been attempted to be achieved by electricaldevices which are complex and may have serious reliability difficulties.The arrangement using simply a natural vortex is not dependent onelectrical components or a large number of moving parts and is thereforesignificantly more reliable.

[0045] An example of actual results is now set out which generally showthe extent of constancy of results thus far obtained. It is of value tosay that the reason the arrangement works so well in the trialsconducted so far is not understood. It is suspected that the dynamicnature of pressure levels within a centripetal vortex are such as tocause this to respond to rapidly changing pressure levels at an outletend with a very rapid change in its low pressure at its inlet end.However, this is a case where it is going to require significant furtherinvestigation to prove any theory.

[0046] The example is now given as follows;

EXAMPLE 1

[0047] The internal combustion engine is a Perkins T4-236 driving a 52kW generator set running at 3000 rpm. The engine has a displacement of3.86 litres and a compression ratio of 16:1. The intake to the enginehas been modified to include a water heated gasifier for LPG andincludes a natural vortex creator in line with the air inlet with liquidpetroleum gas which is fed through the LPG gasifier so that the outletfrom this will then be connected directly to a low pressure centre coreof the natural vortex creator.

[0048] The results are summarised in the following table whichillustrates the consistency in the ratio of fuel power input derivedfrom diesel as compared to total fuel input power of the combined fuelsfor increased loads, where for 20 kW this ratio is 0.35, 30 kW is 0.37and for 40 kW is 0.44.

[0049] Similarly, the percentage LPG by mass of supplemented fuel variedlittle over the range of power outputs, where for 20 kW the fuel wasapproximately 63% LPG by mass, 61% LPG by mass at 30 kW and 54% LPG bymass at 50 kW. The advantages of being able to operate with such highpercentage supplementation are obvious in terms of cost savings.

[0050] Comparison figures for diesel alone are given from which it canbe seen that there are significant reductions in carbon dioxide andnitrous oxide levels in the exhaust when supplementing. Furthermore,there is only a very marginal drop in overall thermal efficiency of theplant when comparing supplementation of fuel with diesel alone for agiven power output. Energy time/ kW of mass of kW of Effi- Diesel ratioLOAD 200 Diesel LPG LPG ciency Mass Diesel/ kW mls kW kg kW % reduc %Total 20 109 64.7 0 0 30.9 100 1.00 20 214 33.0 0.284 61.4 21.2 49.10.35 30  77 91.6 0 0 32.7 100 1.00 30 168 42.0 0.254 70.0 26.8 54.2 0.3740  59 119.6  0 0 33.5 100 1.00 40 125 56.4 0.192 71.1 31.4 52.8 0.44CO2 NO Opacity LOAD CO2 reduc NO reduc red kW % % ppm % Opacity % AFR HC20 6.23 366 16 34.2 0 20 5.8 6.9 221 39.6  4 75.0 30.5 30 8.18 645 3426.6 0 30 7.47 8.7 400 38.0 14 58.8 26.3 40 8.71 938 50 22.7 0 40 7.889.5 553 41.0 33 34.0 23.3 202 

[0051] From these tests, it has been established so far that theconstant ratio over varying loads can be kept substantially constant bythe relatively simple mechanism being described which has significantadvantage through a range of supplementary fuels and other compressionignition internal combustion engines.

[0052] It is found that this arrangement is applicable both to directand indirect injection types of “diesel” engines, and it is alsoapplicable to “diesel” engines which do not have turbo boost. As such,it is therefore even more useful.

1. A method of supplying a fuel supply to a compression ignitioninternal combustion engine which includes having an air supply to theengine first caused to pass through a natural vortex creator, andeffecting a supply of supplementary fuel to the engine by introducingsupplementary fuel into a low pressure area within a central area of anynatural vortex being created by the vortex creator.
 2. A method ofsupplying a fuel supply to a compression ignition internal combustionengine claim 1, further characterised in that a main fuel supply is of ahigh cetane rating and the supplementary fuel is of high octane rating.3. A method of supplying a fuel supply to a compression ignitioninternal combustion engine as in claim 1, wherein the supplementary fuelis being provided at a substantially constant pressure to the lowpressure area within a central area of a natural vortex.
 4. A method ofsupplying a fuel supply to a compression ignition internal combustionengine as in claim 1, further characterised in that the supplementaryfuel is first supplied as a liquid which is introduced into a lowpressure area of a second natural vortex creator which is arranged toeffect a natural vortex with air being drawn through it by the enginewhich then in turn as a vapour is fed into the low pressure area of avortex created by the first said natural vortex creator as thesupplementary fuel.
 5. A compression ignition engine including in itssupply a natural vortex creator, a conduit connecting an outlet of thevortex creator with an air inlet of the engine, a conduit connecting asource of supplementary fuel with the vortex creator so as to have anoutlet of the said conduit communicating with a low pressure center of avortex.
 6. A compression ignition internal combustion engine includingat least one piston within a cylinder, a main fuel injector to effectinjection of fuel into each respective cylinder, means to effect achange in quantity of main fuel being injected into the cylinder inresponse to change in load applied to the engine, a conduit connectingan outlet of a natural vortex creator with an air inlet of the cylinderof the engine, a conduit connecting a source of supplementary fuel withthe vortex creator with its outlet communicating with a low pressurecenter of the vortex creator.
 7. A compression ignition internalcombustion engine including at least one piston within a cylinder, amain fuel injector to effect injection of fuel into each respectivecylinder, means to effect a change in quantity of main fuel beinginjected into the cylinder in response to change in load applied to theengine, a conduit connecting an outlet of a natural vortex creator withan air inlet of the cylinder of the engine, a conduit connecting asource of supplementary fuel in gaseous form with the vortex creatorwith its outlet communicating with a low pressure center of the vortexcreator, means connecting a source of the supplementary fuel as a liquidto a low pressure area of a second natural vortex creator which isarranged to effect a natural vortex with air being drawn through it bythe cylinder, a conduit connecting an outlet of the second naturalvortex creator to a low pressure area of the first said natural vortexcreator.